Recently, as a mobile terminal develops rapidly, a mobile terminal that enables wireless voice communication and information exchange has become a necessity. In an early stage of distribution, a mobile terminal was simply recognized as a product that can be carried and enables wireless communication. As technology develops and a wireless Internet is introduced, the mobile terminal is used not only for the purpose of simple telephone communication or schedule management but also for games, remote control applications using short distance communication, and image capturing by a mounted digital camera, such that its utilization range is expanded.
Furthermore, as digital broadcasting technology develops, a mobile terminal that supports reception of digital broadcasting has been developed to enable viewing of digital multimedia broadcasting while on the move, drawing much attention from users.
Digital multimedia broadcasting may be divided into an encrypted service and an unencrypted service. The unencrypted broadcast service denotes a service that allows a general broadcast viewer to freely view a relevant service according to fixed type ground wave broadcasting. The encrypted broadcast service denotes a service that only allows a user who has obtained a broadcast service use authority to access a relevant broadcasting service according to a subscription-based channel.
The encrypted broadcast service uses the following general encryption scheme. The encryption scheme may include a 3-layer, 2-layer and 1-layer. The 3-layer is an uppermost layer that encrypts a broadcast service and deciphers the encrypted broadcast service. The 2-layer is a middle layer that encrypts a traffic key and deciphers the encrypted traffic key. The 1-layer is a lowermost layer that generates and extracts a service key.
A system that supports the encrypted broadcast service encrypts and transmits a broadcast channel in the 3-layer using an encryption protocol such as Internet Protocol Security (IPSec), Internet Streaming Media Alliance encryption and authentication (ISMACrypt), and so forth.
To decipher encrypted contents of the 3-layer, a traffic key transmitted from the 2-layer is required. Because the traffic key, which is required for deciphering an encryption protocol of the 3-layer, is vulnerable to hacking, it is changed frequently and transmitted with a period of approximately several to tens of seconds. In addition, because the traffic key is encrypted using a service key, which is the 1-layer key, when a mobile terminal that does not have a service key receives a traffic key of the 2-layer, the mobile terminal cannot extract a key required for deciphering an encryption protocol of the 3-layer.
Because the traffic key is transmitted in advance before an encrypted stream, the mobile terminal has a problem of having to stand by for a predetermined time when receiving the encrypted stream that matches with the traffic key. For example, when the mobile terminal receives a ‘No. 3’ traffic key while receiving a  ‘No. 2’ encrypted stream, the mobile terminal has to stand by until receiving a ‘No. 3’stream that can be decrypted using a currently received traffic key, such that a reproduction time of an encrypted channel is delayed.